In recent automobiles, an air bag which is instantly inflated upon a collision of the automobile is often installed as a safety device for alleviating an impact or shock.
FIG. 21 schematically shows a conventional example of a system for controlling inflation of an air bag. In this figure, reference numeral 30 denotes an air bag, 31 denotes an accelerator sensor, for example, 32 denotes an AND gate, and 33 denotes a drive device. More specifically, a switch is provided in a buckle of a seat belt, to be operated when an occupant buckles up or puts on the seat belt, or an infrared sensor is provided around a dashboard of the automobile. The output of the switch or infrared sensor is used to generate a signal indicative of the presence of the occupant. The air bag 30 is inflated when an AND gate 32 receives this signal indicative of the presence of the occupant, along with an accident signal generated by the acceleration sensor 31, and the logical product (AND) of these signals is established in the AND gate 32. The solid line indicates the air bag 30 when it is accommodated in a case, while the broken line indicates the air bag 30 when it is inflated or unfolded.
In the conventional arrangement in which the air bag is inflated without fail if an accident occurs in the presence of an occupant, there arises a new problem that an additional accident may be caused by inflation of the air bag depending upon the posture of the occupant.
Specific examples of this situation are shown in FIG. 22. FIG. 22(a) shows an occupant 2 who sits on a seat while leaning forward, and FIG. 22(b) shows an occupant 2A who is a small child or a baby, for example, when seated in a child seat 5 that faces opposite to the traveling direction of the automobile 3. In these cases, if the air bag is inflation upon occurrence of a collision, the occupant 2 or the small child or baby 2A may be hit by the inflating air bag, possibly resulting in a serious accident. In the case where an occupant is in a normal, safe position as shown in FIG. 23, no accident due to inflation of the air bag occurs when the air bag is inflated.
It is therefore an object of the present invention to avoid an accident due to inflation of the air bag, so as to improve the safety of the air bag system.